The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery, short captions and relevant links.

Sundog and Parhelic Circle

On the photo above, a striking sundog, red on the inside and blue on the outside, shines to the east of the Sun on this early February morning above Urbana, Illinois. The sundog or parhelion is caused by refraction of sunlight through hexagonal ice crystals, most often in cirrus clouds. In addition, a portion of the parhelic circle is also clearly visible. This pale arc, caused by reflection of light from the front faces of oriented crystal, extends further to the east and then continues in the lower picture through a set of stunning icy wisps. To see such delightful colors and arcs, just look up now and then.